A catalytic hydrogen generator is known from EP 0 217 532, which produces hydrogen from a methanol-air mixture in an autothermal reformer unit. Located in the reformer unit is a thermocouple, which controls the supply of air to the methanol-air mixture so that the air supply is reduced as the temperature increases at the location of the thermocouple in the reformer.
International Published Patent Application No. WO 96/00186 describes a hydrogen generator, the catalyst being positioned around an inlet pipe for the methanol-air mixture, so that the methanol-air mixture flows radially through the catalyst.
German Published Patent Application Nos. 43 45 319 and 43 29 323 each describe a fuel-cell current-generating system, in which hydrogen is produced from a methanol-water mixture in a reformer unit. The hydrogen is supplied to a downstream fuel cell for generating electrical energy. To generate a sufficient amount of heat for the reaction in the reformer, a portion of the methanol is not added to the methanol-water mixture but is rather combusted in an additional burner.
An electric vehicle having a driving battery made of fuel cells is described in German Published Patent Application No. 196 29 084, the fuel cells being arranged in such that they are cooled by the wind from driving.
In the article “Heureka?” in DE-Z Autotechnik No. 5/1997, on pages 20 to 21, a motor vehicle having a fuel-cell drive is described, where the hydrogen necessary for operating the fuel cells in the vehicle is obtained from gasoline. In this arrangement, the gasoline is converted into hydrogen in a multi-step process. Prior to conversion, the gasoline is converted into the gaseous state by heating it in an evaporator. Hydrogen and carbon monoxide are formed in a partial-combustion reactor, under oxygen-deficient conditions. Copper-oxide and zinc-oxide catalysts are provided for oxidizing the carbon monoxide, and steam is used to supply oxygen for the reaction. In a further step, a final carbon monoxide fraction of approximately 1% is subsequently burned in a conventional platinum oxidation catalyst. The mixture of hydrogen, carbon monoxide, and carbon dioxide obtained in this manner still contains 10 ppm carbon monoxide, which is not harmful to a downstream fuel cell. After being cooled down to approximately 80 degrees Celsius in a heat exchanger, the gas is supplied into the fuel cell.
A similar fuel-cell system for motor vehicles is described in the article “Alternative Fuel” appearing in the Japanese periodical, Asia-Pacific Automotive Report, Jan. 20, 1998, Vol. 272, page 34 to 39, where a methanol reformer unit is provided to produce hydrogen for a fuel cell. In this arrangement, water produced in the electrochemical reaction of hydrogen and oxygen is reused for the reforming process. For the reforming process, deionized water and methanol are mixed, evaporated, and converted into hydrogen and carbon dioxide at a temperature of 250 degrees Celsius. The hydrogen is supplied to a fuel cell, which, in a catalytic process, converts the hydrogen, together with atmospheric oxygen, into electrical energy and water. The heat energy necessary for the evaporation and for the reforming process is produced in a catalytic burner, which is located downstream from the fuel cell and is run by residual gas from the fuel cell. This gas contains hydrogen, since the fuel-cell system only utilizes approximately 75% of the supplied hydrogen. If an insufficient quantity of residual hydrogen is available for the catalytic burner, methanol from the fuel tank is used to generate heat for the reformer. Before introducing the gas produced in the reformer, of which a portion is hydrogen, this gas is purified by a catalytic reaction, in which carbon monoxide is converted into carbon dioxide. In one embodiment of a fuel-cell system for a motor vehicle, the methanol reformer includes an evaporator, a reformer, and an oxidation unit for carbon monoxide.
German Published Patent Application No. 43 22 765 describes a method and a device for dynamically controlling the power output for a vehicle having a fuel cell, which supplies electrical energy to an electrical drive unit. Starting from a power requirement corresponding to the position of an accelerator pedal, a mass flowrate of air is calculated, which is needed by the fuel cell to provide a corresponding, desired power output. The speed of a compressor positioned in an intake line of the fuel cell is controlled as a function of the required air flow rate.
A method and a device for supplying air to a fuel-cell system is described in European Published Application No. 0 629 013. In this arrangement, process air is compressed by a compressor, before it enters a corresponding fuel cell. After process air flows through the fuel cell, the removed exhaust air is expanded over a turbine, in order to recover energy. The turbine, the compressor, and an additional driving motor are arranged on a common shaft. The compressor is designed to have a variable speed, and is arranged, along with an expander in the form of a turbine, on a common shaft, in order to expand the exhaust air. The air flow rate for the fuel cell is controlled by using an expander having a variable absorption capacity.
A screw-type compressor for a refrigerator is described in International Published Patent Application No. WO 97/16648. The screw-type compressor includes two pump chambers, an outlet of a first pump chamber being connected to a secondary inlet of a second pump chamber.